There is a growing interest in the ability to provide high speed communications links between a ground based communications station and a mobile platform, such as an aircraft, via one or more satellite based transponders. With such systems, the satellite based transponder relays data and other information between users on board the mobile platform and the ground based communications station. One such exemplary system is shown in U.S. patent application Ser. No. 09/989,742, titled, Method And Apparatus For Bi-Directional Data Services And Live Television Programming To Mobile Platforms, filed Nov. 20, 2001, assigned to the assignee of the present application, the disclosure of which is hereby incorporated by reference. Such a system enables a satellite transponder, or a series of satellite based transponders, to provide continuous radio frequency (RF) connectivity between the ground based station and the computing devices being used on the mobile platform by the users while the mobile platform travels within a predefined coverage region.
However, with certain forms of mobile platforms, and particularly with commercial aircraft, which can travel significant distances within a very short period of time, there are expected to be instances where the communications link being provided by the satellite based transponder (or transponders) will be lost temporarily due to the changing location of the aircraft. In these instances, an advance notification system can provide a notification to users on board the mobile platform that the satellite based communications link which the user is using is about to be lost or temporarily interrupted. One such exemplary system is shown in U.S. patent application Ser. No. 10/352,306, filed Jan. 27, 2003, assigned to the assignee of the present application, the disclosure of which is hereby incorporated by reference.
To employ such an advance notification system in a moving mobile platform that can travel into and out of various satellite coverage regions, it is often difficult to determine satellite service availability to the users. Therefore, it would be highly desirable to provide a system and method for determining when a moving mobile platform will enter or exit a satellite coverage region.